A radio frame in a Long Term Evolution (LTE) system includes a frame structure of a Frequency Division Duplex (FDD) mode and a frame structure of a Time Division Duplex (TDD) mode. As shown in FIG. 1, in the frame structure of the FDD mode, one radio frame of 10 ms is composed of twenty slots with the length of 0.5 ms and serial numbers of 0-19, and slots 2i and 2i+1 make up a subframe i with the length of 1 ms (wherein, 0≦i≦9). As shown in FIG. 2, in the frame structure of the TDD mode, one radio frame of 10 ms is composed of two half frames with the length of 5 ms, wherein one half frame includes 5 subframes with the length of 1 ms, and subframe i is defined as the combination of two slots 2i and 2i+1 with the length of 0.5 ms (wherein, 0≦i≦9). The uplink and downlink configurations supported by each subframe are as shown in Table 1, wherein “D” represents subframes dedicated to downlink transmission, “U” represents subframes dedicated to uplink transmission, “S” represents special subframes used in the three domains of Downlink Pilot Time Slot (DwPTS), Guard Period (GP) and Uplink Pilot Time Slot (UpPTS).
TABLE 1Schematic table of uplink and downlink configurationssupported by each subframeUplink-Period ofDownlinkdownlink-configur-uplinkSubframe number #ationswitch point012345678905msDSUUUDSUUU15msDSUUDDSUUD25msDSUDDDSUDD310msDSUUUDDDDD410msDSUUDDDDDD510msDSUDDDDDDD65msDSUUUDSUUD
It can be seen from the above table that the Long Term Evolution (LTE) TDD supports uplink and downlink switch periods of 5 ms and 10 ms. If the period of downlink-to-uplink switch point is 5 ms, then special subframes would exist in two half frames; and if the period of downlink-to-uplink switch point is 10 ms, then special subframes would only exist in the first half frame; the subframe #0 and the subframe #5 and the DwPTS are always used for downlink transmission; and the UpPTS and subframes following the special subframes are dedicated to uplink transmission.
In the LTE TDD system, since the uplink and downlink subframes are not in one-to-one correspondence, that is, the HARQ-ACK information of a plurality of downlink subframes needs to be sent in the Physical Uplink Control Channel (PUCCH)/Physical uplink shared channel (PUSCH) of one uplink subframe, wherein the set of downlink subframes associated with the uplink subframe makes up a bundling window. Two methods of sending the HARQ-ACK information are defined: one is a HARQ-ACK bundling method, and the other is a HARQ-ACK multiplexing method. Whether UE (User Equipment) employs the method of bundling or multiplexing to feed back the HARQ-ACK information is configured by the high-layer. The basic principle of the bundling method is to carry out a logical AND operation (time domain bundling) on the HARQ-ACK information of the code word streams corresponding to respective downlink subframes needing to be fed back in the uplink subframe, to obtain the HARQ-ACK information of ½ bit. When a UE has no PUSCH to send in a current subframe, the UE would employ a format of 1a/1b to send the ½ bit HARQ-ACK information in the PUCCH; and when the UE has PUSCH to send in a current frame, the UE sends the ½ bit acknowledge information in the PUSCH after performing certain channel encoding and channel interleaving on the ½ bit acknowledge information. The core principle of the multiplexing method is to utilize different PUCCH channels and different modulated symbols on each channel to represent different feedback states of the downlink subframes that need to be fed back in the uplink subframe, and if there are a plurality of transport blocks on the downlink subframes, then firstly spatial logic AND (also referred to as spatial domain bundling) is carried out on the HARQ-ACK information fed back by the plurality of transport blocks of the downlink subframes, then channel selection is performed, and then the PUCCH format 1b is used to send the HARQ-ACK information. When the UE has no PUSCH to send in a current subframe, the UE would employ the format 1b with channel selection to send the plurality of pieces of HARQ-ACK information on the PUCCH; and when the UE has PUSCH to send in a current subframe, then the UE multiplexes a plurality of pieces of bit acknowledge information with data after certain mapping from HARQ-ACK states to corresponding bits, channel encoding, channel interleaving are performed to the bit acknowledge information, and then sends them on the PUSCH.
The encoding process when the HARQ-ACK information is transmitted on the PUSCH includes: firstly calculating the number Q′ACK of the symbols needed to be encoded according to the formula
            Q      ACK      ′        =          min      ⁡              (                              ⌈                                          O                ·                                  M                  sc                                      PUSCH                    -                    initial                                                  ·                                  N                  symb                                      PUSCH                    -                    initial                                                  ·                                  β                  offset                  PUSCH                                                                              ∑                                      r                    =                    0                                                        C                    -                    1                                                  ⁢                                                                  ⁢                                  K                  r                                                      ⌉                    ,                      4            ·                          M              sc              PUSCH                                      )              ;wherein O represents the number of bits of the uplink control information to be sent; MscPUSCH represents the bandwidth for PUSCH transmission in a current subframe, and this value is expressed as the number of carriers; NsymbPUSCH-initial represents the number of symbols except for those used for the Demodulation Reference Signal (DMRS) and the Sounding Reference Signal (SRS) in the initial PUSCH transmission; MSCPUSCH-initial represents the bandwidth in the initial PUSCH transmission, and this value is expressed as the number of carriers; C represents the corresponding number of code blocks after the transport blocks are subjected to CRC and code block division; Kr represents the number of bits corresponding to each code block of the transport block; for an identical transport block, C, Kr and MSCPUSCH-initial are obtained from an initial PDCCH; when there is no initial PDCCH with DCI format 0, MSCPUSCH-initial C and Kr could be obtained in the following two ways: (1) when the initial PUSCH employs semi-static scheduling, they could be obtained from the PDCCH configured by the latest semi-static scheduling; (2) when the PUSCH is triggered by a random access response authorization, they are obtained from the random access response authorization corresponding to the same transport block. βoffsetPUSCH represents βoffsetHARQ-ACK or βoffsetRI, the value is configured by the high-layer. Afterwards, channel encoding is carried out on the HARQ-ACK information, and the bits of the encoded HARQ-ACK information are repeated, until a target length QACK=Q′ACK·Qm is satisfied. The bits of the encoded information are respectively recorded as [q0ACK, q1ACK, q2ACK, . . . , qQACK-1ACK], a corresponding encoding modulation sequence [q0ACK, q1ACK, q2ACK, . . . , qQ′ACK-1ACK] is generated according to a modulation order, and [q0ACK, q1ACK, q2ACK, . . . , qQ′ACK-1ACK] and encoded data and/or other encoded uplink control information are transmitted after channel interleaving.
In order to satisfy the requirements of the International Telecommunication Union-Advanced (ITU-Advanced), the Long Term Evolution Advanced (LTE-A) system, as the LTE evolution standard, needs to support a greater system bandwidth (up to 100 MHz), and needs to be backward compatible with the existing standards of the LTE. On the basis of an existing LTE system, a greater bandwidth could be obtained by combining the bandwidths of the LTE system, and such a technique is called a Carrier Aggregation (CA) technique. The technique could improve the spectrum efficiency of an IMT-Advance system, relieve the shortage of spectrum resources, and thus optimizing the utilization of spectrum resources. The bandwidth of the LTE system using the carrier aggregation could be regarded as a Component Carrier (CC), each Component Carrier could also be called a cell, that is, a spectrum could be aggregated by n Component Carriers (n cells). The resources of a R10 terminal (User Equipment, UE) are composed of n cells/Component Carriers in the frequency domain, wherein one cell is called a Primary cell (Pcell), and the rest cells are called Secondary cells (Scells). For the TDD, the uplink and downlink configurations of the aggregated serving cells are the same.
In the LTE-A TDD, when the HARQ-ACK information is sent on the PUCCH, two sending ways are defined: the PUCCH format 1b with channel selection and the PUCCH format3.
It is also defined in the LTE-A that, when uplink and downlink configurations 1-6 are employed and the number of configured serving cells is greater than 1, or when the TDD uplink and downlink configurations 1-6 are employed, the number of the configured serving cells is equal to 1 and the configuration employs the PUCCH format3, the DAI value in the DCI format 0/4 is WDAIUL, and the specific value is as shown in Table 2. If there is no PUSCH transmitted, or, there is no PDCCH indicating downlink release and there is transmission of corresponding DCI format 0/4, WDAIUL=4.
TABLE 2Corresponding WDAIUL values of DAI in the DCI format 0/4DAIHigh bit, low bitWDAIUL0, 010, 121, 031, 14
When the HARQ-ACK information is transmitted over the PUSCH and it is configured to employ the PUCCH format3 to transmit the fed back HARQ-ACK information, for TDD uplink and downlink configuration 0 or PUSCH transmission not performed according to the DCI format 0/4, BcDL=M, wherein BcDL is the number of downlink subframes for which the UE needs to feed back the HARQ-ACK for the serving cell c, and M is the number of downlink subframes in a bundling window; for the TDD uplink and downlink configurations {1, 2, 3, 4, 6} and PUSCH transmission performed according to the DCI format 0/4, BcDL=WDAIUL; and for the TDD uplink and downlink configuration 5 and PUSCH transmission performed according to the DCI format 0/4, BcDL=WDAIUL+4└(U−WDAIUL)/4┘, wherein U represents the maximum Uc of all serving cells, Uc refers to the accumulative number of the PDCCH indicating the SPS release and the PDSCH received on the serving cell c, and if the UE does not receive the PDSCH or the PDCCH indicating downlink SPS release and WDAIUL=4, the UE would not transmit the HARQ-ACK on the PUSCH.
In the subsequent version, when carrier aggregation is supported, the uplink and downlink configurations of aggregated serving cells could be different, that is to say, the numbers of downlink subframes for which the HARQ-ACK information needs to be fed back for respective serving cells are different, in which case, if the existing solution of transmitting HARQ-ACK information on the PUSCH is still employed, transmission of some invalid HARQ-ACK information would be caused. As shown in FIG. 3, assuming WDAIUL=4, the HARQ-ACK information transmitted over the PUSCH according to the existing HARQ-ACK information transmission solution is 8 bits, but the HARQ-ACK information that actually needs to be fed back is only 5 bits, and 3 bits of invalid HARQ-ACK information are transmitted to a base station, thus affecting the performance of HARQ-ACK information and data.